FIG. 15 is a diagram of an infusion line for infusing blood or drug solution through a mixed injection tube for infusion. The blood or drug solution is fed from an infusion solution bottle or bag 300 through an infusion tube 301 to a catheter 303 connected to a connector 302. To one end of the infusion tube 301 is connected an introduction needle 304 to which a drip chamber 305 for monitoring the flow rate of the blood or drug solution is connected. Between the drip chamber 305 and the connector 302, a flow rate adjuster 306, a desired number of mixture injection tubes 307, an air bubble trap 308 for removing dust or air bubbles, and a filter 309 for preventing dust or the like from passing therethrough are connected to the infusion tube 301 (see Japanese Patent Laid-Open Publication No. Hei 8-206230, FIG. 10, for example).
In the conventional mixed injection tube 307, as shown in FIG. 16, a disc-shaped rubber plug 307c is arranged to air-tightly fit into a branch tube portion 307b formed on a side of a T-shaped mixed injection tube main body 307a, for example. A cap 307d is provided to press the rubber plug 307c. The main body 307a of the mixed injection tube 307 is inserted and connected to a middle portion of an infusion tube 301 in an infusion circuit (for example, a dialysis circuit for an artificial kidney, or an intravenous circuit). The mixed injection tube 307 is used for injecting blood or drug solution in a main body of a syringe 310 to blood or drug solution flowing in the infusion circuit, while a syringe needle 310a attached to the syringe 310 is run through the rubber plug 307c fitting in the branch tube portion 307b (see Japanese Patent Laid-Open Publication No. 2002-306610, FIG. 28, for example).
Since this mixed injection tube 307 is used while the syringe needle 310a is run through the disc-shaped rubber plug 307c, the use of the syringe needle 310a increases the cost. Moreover, there is a risk that a doctor or nurse may stick the syringe needle 310a into himself or herself by mistake to be contaminated with pathogenic germs because of adhesion of blood. In addition, in order to prevent pathogenic germs contamination caused by adhesion of blood of a patient, a used syringe needle 310a has to be disposed appropriately without being used again. The disposal of the used syringe needle 310a requires sufficient attention so as not to cause a person who collects disused articles to be improperly damaged by the syringe needle 310a or contaminated with pathogenic germs. Furthermore, the misuse of such a used syringe needle 310a may cause in-hospital infection.
As a connection structure that allows a syringe to be connected without using a needle, the inventors of the present application proposed a structure using a sealing valve made of rubber (see Japanese Patent Laid-Open Publication No. 2002-306610, FIGS. 7 and 8, for example).
Moreover, in recent years, a lock type syringe has been introduced in which a syringe needle is securely held by a screwing structure.
Referring to FIGS. 17a and 17b, a lock type syringe 400 includes a collar 402 surrounding a male connection port 401 (lure portion). In the inner circumferential surface of the collar 402, a double thread female screwing structure 403 is provided. The lock type syringe 400 is used while a syringe needle 405 having a screwing piece 404 at its base end, that is screwed with the double thread female screwing structure 403, is connected to the male connection port 401, as shown in FIGS. 17a and 17c. In FIGS. 17a and 17b, the reference numeral 406 denotes a thread of the female screwing structure 403, 407 a piston of a syringe, 408 a tapered insertion port of the syringe needle 405, having a gradually reduced diameter, and 409 a cylinder portion of the syringe. The male connection port (lure portion) 401 is tapered in such a manner that its outer diameter is gradually reduced from the base end to the top end, and fits with the insertion port 408 of the syringe needle 405 at its tapered face.
As a structure that allows insertion of a lock type syringe without using a needle (i.e., needleless) and also allows opening and closing of a valve, a mixed injection tube has been proposed that includes a valve structure employing a combination of a float and a rubber button (see Japanese Patent Laid-Open Publication No. 2000-354636, for example).
Japanese Patent No. 2954549 proposes connection of a lock type syringe to a drug-solution bag or infusion tube, in a case where drug solution or transfusion is extracted from or injected to the drug-solution bag or the infusion tube that is used for intravenous drip of drug solution or in dialysis treatment. In this connection, the lock type syringe is used without a needle screwed therewith (i.e., needleless).